1. Field of the Invention
The present invention relates to a flexographic preview printer which duplicates conditions of a contemplated printing run on a commercial printing machine. It allows an ink supplier to test its ink under the customer""s printing conditions thereby improving quality control.
2. Brief Description of the Prior Art
In a flexographic printing machine, a plate roller with a raised image is inked with an anilox roller. A substrate is then passed through the nip between a drive roller and the plate roller picking up the reverse of the raised image on the plate roller. Modern flexographic machinery is capable of producing color exacting copies at high speed.
It is well known that the substrate, printing speed and printing pressure and ink metering has an affect on the thickness of the ink film which determines the color achieved on the printed article. Flexographic printing inks must be formulated to provide the desired color under the contemplated printing conditions.
There are hand proofers which apply the ink being tested to the substrate by manually rolling the hand proofers across the substrate. Hand proofers are not capable of providing consistent results because of three major variables. First, the speed with which the operator rolls the hand proofer varies from operator to operator and even with the same operator. Second, the pressure with which the operator presses the hand proofer onto the substrate varies in the same way. Third, there is no mechanism for consistent metering of the ink on the anilox roller. Because of these variables, it is virtually impossible to obtain repeatable proofs, i.e. proofs which are substantial duplicates of each other, even when the same operator uses the same hand proofer and the same ink.
There are manual and automated proofers but none of them effectively simulate the exact press speed and pressure of a flexographic printer (i.e., they do not duplicate the same conditions encountered in a press run).
In view of the above, it is an object of the present invention to provide a preview printer that duplicates conditions of a contemplated press run. It is another object to provide a preview printer for testing a printing ink under the customer""s printing conditions thereby improving quality control. It is also an object to provide a preview printer that is easy to clean between tests. Other objects and features of the invention will be in part apparent and in part pointed out hereinafter.
In accordance with the invention, a flexographic preview printer has an inking unit and a printing unit. The inking unit has an inking roller in contact with an anilox roller for transferring ink from the inking roller to the anilox roller and a doctor blade for precision metering of the ink on the surface of the anilox roller. The printing unit has a plate roller with an image to be printed and a drive roller for moving a substrate through a nip between the drive roller and the plate roller with the nip adjustable to the thickness of the substrate.
The inking unit is powered by a first gear train connected to a first motor through a throw-out clutch. The first motor is initially activated and adapted to rotate the inking roller and the anilox roller at a set slow speed.
The printing unit is powered by a second gear train meshed with the first gear train through a throw-in clutch and driven by a second motor. The second motor is initially inactivated and adapted to rotate the plate roller and the drive roller at an adjustable speed that is higher than the speed at which the first motor rotates the inking roller and the anilox roller. The second motor is activated when said anilox roller is selectively brought into contact with the plate roller. The anilox roller being in a rotational ratio of one to one with the plate roller.
The second motor drives the second gear train and the second gear train drives the first gear train through the throw-in clutch when the second motor is activated. The first gear train is disengaged from the first motor through the throw-out clutch when the first gear train is driven by the second gear train. In operation, the inking unit is rotated at a set slow speed by the first motor and then disengaged from the first motor when the second motor is activated rotating the printing and inking units at an adjustable faster speed.
The invention summarized above comprises the constructions hereinafter described, the scope of the invention being indicated by the subjoined claims.